feat: Add external stock fields for product variations in WooCommerce

includes/class-siti-stock-inventory-manager.php

@@ -27,6 +27,8 @@ class Siti_Stock_Inventory_Manager {
 	public function register_hooks() {
 		add_action( 'woocommerce_product_options_stock_fields', array( $this, 'render_external_stock_field' ) );
 		add_action( 'woocommerce_admin_process_product_object', array( $this, 'save_external_stock_value' ) );
+		add_action( 'woocommerce_variation_options_inventory', array( $this, 'render_variation_external_stock_field' ), 10, 3 );
+		add_action( 'woocommerce_save_product_variation', array( $this, 'save_variation_external_stock_value' ), 10, 2 );
 		add_filter( 'woocommerce_product_get_stock_quantity', array( $this, 'filter_stock_quantity_with_external' ), 10, 2 );
 		add_filter( 'woocommerce_product_variation_get_stock_quantity', array( $this, 'filter_stock_quantity_with_external' ), 10, 2 );
 		add_filter( 'woocommerce_product_get_stock_status', array( $this, 'filter_stock_status_with_external' ), 10, 2 );
@@ -87,6 +89,67 @@ class Siti_Stock_Inventory_Manager {
 		$product->update_meta_data( $this->external_stock_key, $value );
 	}
 
+	/**
+	 * Render the external stock field for each variation row.
+	 *
+	 * @param int        $loop           Loop index.
+	 * @param array      $variation_data Raw variation data.
+	 * @param WP_Post    $variation      Variation post object.
+	 */
+	public function render_variation_external_stock_field( $loop, $variation_data, $variation ) {
+		unset( $variation_data );
+
+		if ( ! function_exists( 'woocommerce_wp_text_input' ) ) {
+			return;
+		}
+
+		$product = $variation instanceof WC_Product ? $variation : wc_get_product( $variation->ID );
+
+		if ( ! $product instanceof WC_Product ) {
+			return;
+		}
+
+		$external_stock = $this->get_external_stock( $product );
+		$field_key      = 'variable_' . $this->external_stock_key;
+
+		woocommerce_wp_text_input(
+			array(
+				'id'                => $this->external_stock_key . '_' . $loop,
+				'name'              => $field_key . '[' . $loop . ']',
+				'value'             => $external_stock,
+				'label'             => __( 'Externe voorraad', 'siti-stock-plugin' ),
+				'desc_tip'          => true,
+				'description'       => __( 'Voorraad beschikbaar op externe locatie(s).', 'siti-stock-plugin' ),
+				'type'              => 'number',
+				'wrapper_class'     => 'form-row form-row-full',
+				'custom_attributes' => array(
+					'step' => '1',
+					'min'  => '0',
+				),
+			)
+		);
+	}
+
+	/**
+	 * Persist external stock for variations.
+	 *
+	 * @param int $variation_id Variation post ID.
+	 * @param int $index        Loop index.
+	 */
+	public function save_variation_external_stock_value( $variation_id, $index ) {
+		$field_key = 'variable_' . $this->external_stock_key;
+
+		if ( ! isset( $_POST[ $field_key ][ $index ] ) ) { // phpcs:ignore WordPress.Security.NonceVerification.Missing
+			return;
+		}
+
+		$raw_value = wp_unslash( $_POST[ $field_key ][ $index ] ); // phpcs:ignore WordPress.Security.NonceVerification.Missing
+		$value     = function_exists( 'wc_stock_amount' ) ? wc_stock_amount( $raw_value ) : (int) $raw_value;
+		$value     = max( 0, (int) $value );
+
+		update_post_meta( $variation_id, $this->external_stock_key, $value );
+	}
+
 	/**
 	 * Ensure WooCommerce exposes combined stock (local + external) on the frontend.
 	 *